In mammals, there are approximately 100,000 genes which govern the development of an organism. For development, to proceed normally, there must be coordinate interaction of thousands of these gene products in many given cell of the being. Beginning with fertilization, precise expression of these gene products is required during embryonic, fetal, post-natal, and adult development. Aberrant synthesis of even one of these gene products can be disastrous-birth defects, cancer infertility, and even death are all possible when this developmental program is altered. For the last few years, studies in my laboratory have been directed at elucidating the critical gene products involved in both normal and abnormal mammalian reproductive development. Using ES cell technology, we have created several mouse models which have female reproductive defects. Female mice deficient in growth differentiation factor-9 (GDF-9), follicle stimulating hormone (FSH), and activin receptor type II (ActRII) are infertile due to blocks at specific stages of folliculogenesis. Using a cDNA subtractive hybridization approach, we have taken advantage of differences between the ovaries of wild-type and GDF-9 deficient mice to identify novel cDNAs expressed in the ovary with no known function. By Northern blot and in situ hybridization analysis, we have shown that at least three of these cDNAs are specifically expressed in the wild- type ovary in either the oocyte or the granulosa cells. This proposal will focus on the further identification of novel ovarian cDNAs and genes, and the initial steps toward the generation of knockout mouse models lacking these ovary-specific gene products. The Specific Aims are as follows: 1) Isolation and characterization of novel cDNAs expressed in the ovary, 2) Isolation of full-length ovarian cDNAs and genes, and 3) Generation of knockout mice lacking novel ovarian genes. The studies described above are out initial inroads into the identification, characterization, and functional analysis of novel ovary-specific genes. Female transgenic mice lacking these ovarian gene products are anticipated to be infertile or possibly demonstrate increased fertility. If this hypothesis is true, these studies will give us key insights into possible genes implicated in human idiopathic infertility, may allow us to develop new contraceptive agents and treatments for human infertility, and will permit us to seek R01 funds for continuing this important fertility-related research.